Process for making films and the



Aug. 25, 1936. H. F. ROBERTSON Re. 20,

PROCESS FOR MAKING FILMS AND THE LIKE AND PRODUCTS THEREBY MADE Original Filed Nov. 22, 1935 VINYL V SOLVENT RESIN VINYL RESIN SOLUTION ORIFICE NON-SOLVENT I BAT H I SOLVENT I A u o NON-SOLVENT SEPARATION DQIER I FINISHED FILM IINVENTOR HADOLD FDOBEPTSON.

ATTORNEY Reissued Aug. 25, 1936 PATENT OFFICE-T PROCESS FOR MAKING FILMS AND THE LIKE AND PRODUCTS THEBEBY MADE.

Harold F. Robertson, Coraopolis, Pa., alsignor,

by meene assignments, to Union Carbide and Carbon Corporation, a corporation of New York Original No. 2,010,903, dated August 13, 1985,

Serial No. 899,100, November 22. 1933. Application for reissue June 19, 1936, Serial No.

20 Claims.

The present invention pertains to the production of film, webs, sheets, filaments and the like from vinyl resins and vinyl resin compositions.

Vinyl resins, that is, artificial resinous products obtained by the polymerization of certain vinyl compounds, are known and havebeen pro- .posed for many uses. It has been proposed to,

make thin sheets or webs from vinyl resin compositions, but the means proposed for producing this form of product have been unsatisfactory,

1 and have never been adapted to the successful manufacture of vinyl resin films or the like. In general, the previously proposed methods for making thin sheet products from vinyl resins have comprised either plating out a solution of the resin on a smooth surface and stripping therefrom the film formed upon drying, or pressing thin portions of solid resin between heated platens or calender rolls. In addition to these methods which have been attempted, Patent No. 1,241,738 to Klatte and Rollett states that solutions of vinyl acetate polymers may be squirted into a precipitating agent, such as alcohol or ether, to form a product in thread form.

So far as I am aware, none of these methods have been used on a large scale for the formation of vinyl resins in the form of thin sheets, films, webs or filaments. Obviously, from the standpoint of economy and flexibility of operation, the most desirable method to use 'would comprise the precipitation of the resin in the desired form from a solution, but despite the teaching of the Klatte et al. patent this is not possible as therein described. When .a stream of a solution of vinyl resin is added to a non-solvent or a precipitating agent, the latter displaces the solvent and the resin is precipitated as a white opaque mass in the form of the stream of solution which was added to the no solvent, but it will not be a clear, transparent or usable film.

The principal object of my invention is to provide a new process for making films, webs, sheets, filaments and the like from vinyl resins and to make available these new films, etc. Another object is to provide method for making films, webs, sheets, filaments and the like from vinyl resins which employs a solution of the resin and a precipitating agent or non-solvent. Another object is to provide a new process for spinning vinyl resins to form useful threads and filaments. I have found by experimentation that I am enabled to achieve successfully the objects of the invention by selecting particular conditions under which the extrusion, spinning or squirting ofa vinyl resin solution into a bath of non-solvent or a precipitating agent is conducted. In general, these conditions comprise passing a shaped stream of vinyl resinsolution into a bath of precipitating agent or non-solvent for the resin and-removing the stream of vinyl resin from the bath at a rate which prevents the removal by the non-solvent of all the solvent in the stream of .vinyl resin solution, but which permits the removal of sumcient solvent to cause the stream of vinyl resin to coagulate on the surface and become coherent. The stream thus solidified enough to assume a definite shape is treated to remove the balance of solvent from its interior and the removal of this residual solvent likewise 15 removes any non-solvent from the surface. A self-supporting continuous, smooth, hard, and coherent body of vinyl resin is thus obtained which is in the form given to the initial stream of the solution, and which is self-glossed and polished by the action of the solvent removal.

The process is well adapted for a continuous process of manufacturing films, webs, sheets, filaments, threads or the like from vinyl resins. Any vinyl resin which has physical properties suitable for the particular form being made may be used in my new process. Since the process is primarily useful for making forms of vinyl resins in which at least one dimension of the final form produced is very small, the resin used in the process must be tough, flexible and strong enough to be useful when made into forms'of minute dimensions. I prefer to use those vinyl resins which are made by conjointly polymerizing two or more vinyl derivatives, of which vinyl halides, particularly the chloride, vinyl esters of aliphatic acids, such as vinyl acetate, propionate and butyrate, and vinyl benzene or styrene are illustrative. Particularly desirable vinyl resins are those resulting from the conjoint polymerization of vinyl chloride and vinyl acetate in the proportions of from about 70 to 93 parts of vinyl chloride with about 30 to 7 parts of vinyl acetate.

may be prepared by special methods of polymerization, for instance, by conducting the polymerization reaction at temperatures below 0.,

preferably below 40 C., with a small amount of r catalyst, and in the presence or absence of solvents or liquid media. However, if liquid media are employed they should be chosen from those substances which are non-solvents or poor solvents for vinyl resins, and as little as possible-of the liquid should be used, Vinyl resins and processes of making them are not a part of this invention. TY

The following detailed description will .iilustrate the mode of practicing my invention, but these illustrations are not to be considered'as limitations on the invention. The flow ofmate'- rials in the process may be as shownin the accompanying drawing.

A'vinyl resin was prepared by conjointly polymerizing vinyl chloride and vinyl acetate in the absence of any liquid medium or solvent other than the vinyl compounds. The temperature during the polymerization was maintained at about 30 C. Benzoyl acetyl peroxide in an amount equal to about 0.4% by weightof the vinyl-compounds was used as a catalyst. The resin obtained contained about 85% of vinyl chloride in the conjoint polymer, and was dissolved in acetone and filtered free of suspended matter to obtain a clear, substantially water-white solution. The solution of resin in acetone was then made into film by extruding the solution by pneumatic pressure from a reservoir through an extrusion slit into water as a precipitating agent. The temperature of the water was kept at about 35- C. Air pressure in'varying amounts was used to efl'ect the extrusion. As before noted, the film formed was white and opaque and could not be dried at the temperatures used to give a clear transparent film if it was allowed to remain in the precipitating bath. The period which the film remained in the precipitating bath was regulated by the linear speedof extrusion, and was adjusted to be' such as to make the film just coherent and strong enough for handling, (i. e; capable of self-support) as it left the precipitating bath. From the precipitating "bath the film was passed through a horizontal drier heated by a current of hot air. The temperature in the drying tower was about 50 C. to 60 C. The remaining solvent, and any of the water from the precipitating bath which was in the film was here removed, and the driedfilm was rolled 'onto spools. The finished product was clear, flexible and transparent and possessed good strength.

The table below shows operating data ofthe process illustrating the eilect of -the several variables. y

Solvent Acetone Precipitating bath Water Orifice 0.0100 x 7 inches Conan Viscosity tration of solution Air was Film Tension Dry fllm solution, see at sura,ibs./ speed, on film, thickness, resitn by sq. in. ftJmin. lbs. inches w The viscosity figures were obtained by measuring thetime required for a steel'ball having a diameter of 0.1875 inch to fall through centimeters of the solution.

The tension referred to is that iorce applied to the dried and cooled film and is effective between the drier discharge and the reel for the finished In these operations the drying temperature was between 50 and'iOf'C.

The precipitating bath may be used satisfactorily until it contains asmuch as 75%acetone. The acetone-water mixtures obtained from the precipitating bath and the drying tower may be fractionated in the usual way to recover the two materials for reuse. It will be apparent that by regulating the film speed the period which the resin stream remains in the precipitating bath can be adjusted to produce the proper degree of precipitation regardless of the size of the bath. The temperature of the precipitating bath has an efiect upon the quality of film produced. For example, if the bath is at a low temperature, precipitation is slow and the resulting film may exhibit striations. Therefore, it .is desirable to eflect precipitation as rapidly as possible. I have found that precipitation will occur at any temperature in the bath between 0 and 50 C., but I prefer the range of about 25 to 35 0., and temperatures of about 35 C. are desirable.

It is possible to produce thicker film, that is, in thicknesses up to 0.007 or 0.008 inch, by increasing the content oi. vinyl resin in the solution. For example, aisolution containing about 70% vinyl resin may be used, but since such a solution at ordinary temperatures is a thick gel, it must be heated and extruded while maintaining its temperature suiliciently high to prevent gel formation, for example, at about 60 C. Informing film from these concentrated solutions, greater air pressure may be used on the vinyl resin solutions. Pressures of 40 pounds per square inch or even greater have been used satisfactorily.

Other solvents and. precipitating agents may be used. In general, any solvent for the vinyl 'resin may be used, and any non-solvent may serve with the particular solvent employed. Preferably,

to expedite precipitation, the solvent and nonsolvent used are selected so that they are completely miscible. Examples of solvents are: ketones, such as methyl ethyl ketone,idipropyl ketone, cyclohexanone and methyl butyl ketone; cyclic dialkylene dioxides, such as l.4 dioxane and dimethyl dioxane; esters, such as ethyl acetate and butyl acetate; halogenated hydro-carbons, such as chlorbenzene, ethylene and propylene dichlorides or dibromides and acetylene tetrachloride; and aromatic hydrocarbons, such as toluene and xylene. Suitable non-solvents are: water, paraflin hydrocarbons, such as pentane, hexane and heptane; aliphatic alcohols, such 'as methanol, ethanol, isopropanoland ethylene glycol; and aliphatic ethers, such as diethyl, disopropyl and dibutyl ethers.

The vinyl resin solution may have modifying substances incorporated therein to vary specific properties of the film. For example, plasticizers, such as dibutyl phthalate, di (ethylene glycol monobutyl ether) phthalate, tricresyl phosphate, chlorinated naphthalenes and diphenyl derivatives to makethe film more flexible; waxes may be added to increase the moisture resistance of the, film and to decrease any tendency to tackiness; dyes or pigments may be added to produce 7 colors and varying degrees of translucency or opacity: or other known modifying agents may beaddedtotheresin. Inthisconnection.apa.r-

tieular advantage inures to the use of water as a precipitating agent, since it is possible to .use modifying substances in the resin which might be partially or wholly extracted by media, such as alcohols or ethers, and which are unafi'ected by water, The plasticizers may be used-in any amount up to about 20% or somewhat more based on the weight of vinyl resin. About 18% of di (beta-butozw ethyl) phthalate has been found to be very successful in producing flexible films which are readily produced by my process, and which are not tach. waxes may be used in amounts less than 2% by weight of the vinyl resin, and a preferred quantity is about 0.5%. Suitable waxes are those composed largelyof parafiin hydrocarbons, such as paramn wax. ceresin wax, japan wax and the like. The addition of wax greatly increases the moisture resistance of thefilm. For example, a film containing 0.5% paraffin wax and 18% di (beta-butory ethyl) phthalate was found to transmit moisture at a rate only one-third as great as that of 1mmodifled film.

The wax may be best incorporated in the film by forming a solution of it in a wax solvent, such as toluene, monochlorbenzene, benzene, or the like, and this solution is then added to the vinyl resin solution. Necessarily, this results in a vinyl resin solution which contains a few' per cent. of water-insoluble solvent, but I havefound that this does not interfere with proper precipitation of film in a water-precipitating bath.

The surfaces of the rolls, guides and other mechanical parts of the film forming equipment may be lubricated to facilitate slipping of the film thereover. As lubricants, I prefer to use alcohols or alcoholic compositions. The alcohols used should be relatively non-volatile at the temperatures used for drying the film, and must be capable of spreading andwetting the m or roll surfaces. I prefer to use polyhydric alcohols 01 high boiling point together with monohydric alcohols to prevent coalescence of the lubricant on the surfaces. Ethylene and propylene glycols or poly glycols and glycerine are suitable polyhydric alcohols, and butyl, amyl, hexyl and octyl alcohols are suitable monohydric alcohols. A useful lubricant may be a mixture of diethylene glycol and butyl alcohol. The lubricant is preferably removedfrom the film by washing or otherwise before it is reeled into rolls. cant is essential, for otherwise the handling of the film on heated rolls would be exceedingly diflicult.

Drying temperatures up to about 110 C. may be used, and the heat may be applied to the film in any desired manner. I prefer to use a current of heated air supplied countercurrent to the dithreads, filaments and all like Phy ical forms'in I which at least one dimensions! the cross-section is small.

The use of a lubri- This application contains subject matter in common with my application Ber. No. 853,485,

filed January 25, 1933. v

Iclaimz- 1. Process of making films-from vinyl resins which comprises forming a shaped stream'o'f a vinyl resin-containing solution, passing said shaped stream into'a precipitating bath containing a liquid which is a non-solvent for the vinyl resin and which is at least partially miscible with the solvent in said solution, removing said shaped stream from said bath at a rate which permits bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape, thereafter drying said shaped stream by means of heated air to eliminate solvent and non-solvent therefrom.

3. .Procem of making films from vinyl resins which comprises forming a solution containing a vinyl resin. forcing the solution by pneumatic pressure through an orifice to form a shaped stream of vinyl resin-containing solution, passing said shaped stream into a precipitating bath containing a liquid which is a non-solvent for the vinyl resin and which is at least partially miscible with the solvent in said solution, removing said shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape, thereafter drying said shaped stream by means of air heated between about 50 and about 110 C. to eliminate solvent and non-solvent therefrom.

4. Process for making films from vinyl resins which comprises forming a vinyl resin solutionin acetone, forcing the solution through an orifice to form a shaped stream of vinyl resin-containing solution, passing said shaped stream into a precipitating bath containing a liquid which is miscible with acetone and which is a non-solvent for the vinyl resin, removing said shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape, and thereafter drying said shaped stream to eliminate acetone and the non-solvent therefrom.

5. Process for making films from vinyl resins which comprises forming a vinyl resin solution in acetone, forcing the solution through an orifice fice to form a shaped stream of vinyl resincontaining solution, passing said shaped stream into a precipitating bath containing water, removing said shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its'shape, and thereafter drying said shaped toeliminate acetone and the water therefrom.

6 Processfor making films from vinyl resins which comprises forming a solution in acetone of a vinyl resin substantially identical with a resin resulting from the conjoint polymerization of vinyl chloride and vinyl acetate, forcingv the solution through an orifice to form a shaped stream of vinyl resin-containing solution, passing said shaped stream into a precipitating bath containing water, removing said shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape,

and thereafter drying said shaped stream to eliminate acetone and the water therefrom.

8. Process for making films from vinyl resins which comprises forming a solution in acetone of a vinyl resin substantially identical with a. resin resulting from the conjoint polymerization of vinyl chloride and vinyl acetate in the proportions of at least about 80% of the chloride, forcing the solution through an orifice to form a shaped stream of vinyl resin-containing solution, passing said shaped stream into a precipitating bath containing water, removing s'a'id shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape, and thereafter drying said shaped stream to eliminate acetone and the water therefrom.

9. Process for making films from vinyl resins which comprises forming a solution in acetone of a vinyl resin and a plasticizer therefor, forcing the solution through an orifice to form a shaped stream of vinyl resin-containing solution, passing said shaped stream into a precipitating bath containing water, removing said shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape, and thereafter drying said shaped stream to eliminate acetone and the water therefrom. 10. Process for making vinyl resin films which comprises forming a solution in acetone of a vinyl resin substantially identical with a resin resulting from the conjoint polymerization of vinyl chloride and vinyl acetate .in the proportions of at least about 80% of the chloride, forcing the solution by pneumatic pressure through an orifice to form a shaped stream of vinyl resincontaining solution, passing said shaped stream into a precipitating bath containing at least about 25% of water, removing said shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape, and thereafter subjecting said stream to air heated between about 50 and about 110 C. to eliminate acetone and water therefrom.

11. Process for making vinyl resin-films which comprises forming a solution in acetone of a vinyl resin substantially identical with a resin resulting from the conjoint polymerization of vinyl chloride and vinyl acetate in the proportions of at least about 80% of the chloride, forcing ao,oso

the solution by pneumatic pressure through an orifice to form a shaped stream of vinyl resincontaining solution, passing said shapedstream I 12. Process for making film from vinyl resins" which comprises forming a solution in acetone containing a vinyl resin identical with a resin resulting from the conjoint polymerization of a vinyl halide and a vinyl ester of an aliphatic acid. a plasticizer and a wax; forcing the solution by pneumatic pressure through an orifice to form a shaped stream of said vinyl resin-containing solution; passing said shaped stream into a precipitating bath containing at least 25% of water; removing said shaped stream from said bath at a rate which permits the resin in said stream to precipitate only to an extent which will cause the shaped stream to retain its shape, and thereafter eliminating acetone and water therefrom.

13. A flexible, non-tacky film composed of a vinyl resin identical with a resin resulting from the conjoint polymerization of a vinyl halide and a. vinyl ester of an aliphatic acid, said film being capable of self-support, continuous, smooth, hard support, continuous, smooth, hard and coherent,

and being self-glossed and polished by the removal of solvent and non-solvent liquid media from said film after it is formed.

15. A fiexible,,non-tacky film composed of a vinyl resin ,and a wax, said film being capable of self-support, moisture-resistant, continuous, smooth, hard and coherent, and being self-glossed and polished by the removal of solvent and nonsolvent liquid media from the-film after it is formed.

16. A flexible non-tacky film composed of a vinyl resin identical with. a resin resulting from the conjoint polymerization of vinyl chloride and vinyl acetate in the proportions of at least about 80% of the chloride, together with about 18% di (beta-butoxy ethyl) phthalate and 0.5% paraifin wax based on the weight of vinyl resin; said film being capable of self-support, moisture-resistant, continuous, smooth, hard and coherent, and being self-glossed and polished by the removal of solvent and non-solvent liquid media from the film after it is formed.

17. Process for making films from vinyl resins which includes the step of removing solvent and non-solvent from the partly formed film by sub jecting said film to heat while it is supported upon'surfaces lubricated with an alcoholic composition.

18. Process for making films from vinyl resins which includes the step of removing solvent and non-solvent from the partly formed film by subjecting said film to heat while it is supported upon surfaces lubricated with an alcoholic composition which is relatively non-volatile at the drying temperature employed.

19. Process for making films from vinyl resins which includes the step or removing solvent and non-solvent from the partly gtormed film by subjecting said film to heat while it is supported upon surfaces lubricated with an alcoholic composition which comprises polyhydric alcohols together with monohydric alcohols.

20. Process for making films from vinyl resins which includes the step of removing solvent and non-solvent from the partly formed film by subjecting said film to heat while it is supported upon surfaces lubricated with an alcoholic composition whichcomprises at least one" alcohol from the group consisting of ethylene glycol, polyethylene glycols, propylene giycol,.- poly propylene glycols, and glycerine together with a monohydric alcohol from the group consisting of butyl; amyl, hexyl and octyl alcohols.

HAROLD F. ROBERTSON. 

